Doxygenized some functions in vout_pictures.c. Prepared for new chroma

fourcc YUVA to be used in subpicture rendering

include/vlc_video.h

@@ -165,6 +165,7 @@ struct picture_heap_t
 #define Y_PLANE      0
 #define U_PLANE      1
 #define V_PLANE      2
+#define A_PLANE      3
 
 /* Shortcuts */
 #define Y_PIXELS     p[Y_PLANE].p_pixels

src/video_output/vout_pictures.h

@@ -2,7 +2,7 @@
  * vout_pictures.h : picture management definitions
  *****************************************************************************
  * Copyright (C) 2002-2004 VideoLAN
- * $Id: vout_pictures.h,v 1.6 2004/02/27 14:01:35 fenrir Exp $
+ * $Id$
  *
  * Authors: Samuel Hocevar <sam@zoy.org>
  *
@@ -88,3 +88,5 @@
 /* Planar 4:4:4, Y:U:V */
 #define FOURCC_I444         VLC_FOURCC('I','4','4','4')
 
+/* Planar 4:4:4:4 Y:U:V:A */
+#define FOURCC_YUVA         VLC_FOURCC('Y','U','V','A')